In article ,
Scott Dorsey wrote:
So, if I adjust the voltage on the suppressor grid of a pentode I can alter
the gain of the tube substantially, but in the process I now am moving most
of the current from the plate to the screen grid.

Are there any tubes out there with a sufficiently heavy screen grid that
this could be done with? I can always reduce the total current to prevent
screen grid damage but then linearity suffers.

Do any small signal pentodes out there exist with heavy ruggedized screen
grids?
--scott

Coming into this late, as I don't often read this newsgroup any more.

Scott, you need a power pentode with a separate supressor terminal.
RCA made one: 6AG7. Overall, similar characteristics to a 50L6, but a
pentode, not a beam tetrode.

You're on your own working out the Gm and Mu curves for G2 and G3.
RCA came up with the tube, along with the 1851,1852,and 1853, for prewar
TV video amplification.

Hank